• Authors:
    • Pal, M.
    • Chakraborty, D.
    • Sehgal,V. K.
    • Saha, S.
  • Source: Agriculture Journal
  • Volume: 203
  • Year: 2015
  • Summary: Experiments on chickpea ( Cicer arietinum L.) were performed in open-top chambers during 2010-11 and 2011-12 to assess effects of atmospheric CO 2 enrichment on the quality of seeds. Although no physical modification was observed, an increase in seed water uptake was recorded in plants grown under enriched atmospheric CO 2 condition. Germination of seeds reduced by 45-47%, while seed leachate conductivity increased by 10-17%. Seedling vigor decreased, although root and shoot lengths and seedling biomass showed negligible changes. Similarly, atmospheric CO 2 enrichment reduced field emergence of seedlings with no change in root characteristics of the emerged seedlings. A decrease in protease activity supports the reduced seed viability, although no change in grain phosphatase and alpha-amylase activities were recorded. Increase in carbon content in germinating seed-cotyledon along with decrease in N in cotyledon resulted in large increase in C:N ratio for the plants grown under enriched CO 2 condition. The starch content increased with no change in soluble sugar in germinating seed-cotyledons. This indicates more carbonaceous seeds from plants grown under enriched CO 2 environment. Results suggest that rising atmospheric CO 2 might have adverse impact on viability and germination of chickpea seeds, and cause nutritional imbalance through increase in C with dilution of N contents in germinating seed-cotyledons.
  • Authors:
    • Rubenstein, D.
    • Notenbaert, A.
    • Beringer, T.
    • Thornton, P. K.
    • Estes, L.
    • Searchinger, T. D.
    • Heimlich, R.
    • Licker, R.
    • Herrero, M.
  • Source: Article
  • Volume: 5
  • Issue: 5
  • Year: 2015
  • Summary: Do the wet savannahs and shrublands of Africa provide a large reserve of potential croplands to produce food staples or bioenergy with low carbon and biodiversity costs? We find that only small percentages of these lands have meaningful potential to be low-carbon sources of maize (1/42%) or soybeans (9.5-11.5%), meaning that their conversion would release at least one-third less carbon per ton of crop than released on average for the production of those crops on existing croplands. Factoring in land-use change, less than 1% is likely to produce cellulosic ethanol that would meet European standards for greenhouse gas reductions. Biodiversity effects of converting these lands are also likely to be significant as bird and mammal richness is comparable to that of the world's tropical forest regions. Our findings contrast with influential studies that assume these lands provide a large, low-environmental-cost cropland reserve. © 2015 Macmillan Publishers Limited. All rights reserved.
  • Authors:
    • Lobell, D.
    • Schlenker, W.
    • Roberts, M.
    • Urban, D.
  • Source: Journal
  • Volume: 130
  • Issue: 2
  • Year: 2015
  • Summary: Short durations of very high spring soil moisture can influence crop yields in many ways, including delaying planting and damaging young crops. The central United States has seen a significant upward trend in the frequency and intensity of extreme precipitation in the 20th century, potentially leading to more frequent occurrences of saturated or nearly saturated fields during the planting season, yet the impacts of these changes on crop yields are not known. Here we investigate the yield response to excess spring moisture for both maize and soybean in the U.S. states of Illinois, Iowa, and Indiana, and the impacts of historical trends for 1950-2011. We find that simple measures of extreme spring soil moisture, derived from fine-scale daily moisture data from the Variable Infiltration Capacity (VIC) hydrologic model, lead to significant improvements in statistical models of yields for both crops. Individual counties experience up to 10 % loss in years with extremely wet springs. However, losses due to historical trends in excess spring moisture measures have generally been small, with 1-3 % yield loss over the 62 year study period.
  • Authors:
    • Daigh,A. L.
    • Sauer,T.
    • Xiao,X. H.
    • Horton,R.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 3
  • Year: 2015
  • Summary: Models of instantaneous soil-surface CO 2 efflux (SCE ins) are critical for understanding the potential drivers of soil C loss. Several simple SCE ins models have been reported in the literature. Our objective was to compare and validate selected soil temperature ( Ts)- and water content (theta v)-based equations for modeling SCE ins among a variety of cropping systems and land management practices. Soil-surface CO 2 effluxes were measured and modeled for grain-harvested corn ( Zea mays L.)-soybean [ Glycine max (L.) Merr.] rotations, grain- and stover-harvested continuous corn systems with and without a cover crop, and reconstructed prairies with and without N fertilization on soils with subsurface drainage. Soil-surface CO 2 effluxes, Ts, and theta v were measured from 2008 to 2011. Models calibrated with weekly measured SCE ins, Ts, and theta v throughout the growing season produced lower root mean squared error (RMSE) than models calibrated with several weeks of hourly measured data. Model selection significantly affected SCE ins estimations, with models that use only Ts parameters having lower RMSE than models that use both Ts and theta v. However, the model that produced the lowest RMSE during validation estimated growing-season SCE that did not significantly differ from numerical integration of weekly measured SCE ins. All models had similar residual errors with autocorrelated trends at monthly, weekly, and hourly scales. Autoregressive moving average functions were able to precisely describe the temporal errors. To accurately model SCE ins and scale across time, improvement of temporal errors in Ts- and theta v-based SCE ins models is needed to obtain accurate and precise closure of C balances for managed and natural ecosystems.
  • Authors:
    • Zuber,S. M.
    • Behnke,G. D.
    • Nafziger,E. D.
    • Villamil,M. B.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 3
  • Year: 2015
  • Summary: Recent increases in corn ( Zea mays L.) production in the U.S. Corn Belt have necessitated the conversion of rotations to continuous corn, and an increase in the frequency of tillage. The objective of this study was to assess the effect of rotation and tillage on soil physical and chemical properties in soils typical of Illinois. Sequences of continuous corn (CCC), 2-yr corn-soybean [ Glycine max (L.) Merr.] (CS) rotation, 3-yr corn-soybean-wheat ( Triticum aestivum L.) (CSW) rotation, and continuous soybean (SSS) were split into conventional tillage (CT) and no-till (NT) subplots at two Illinois sites. After 15 yr, bulk density (BD) under NT was 2.4% greater than under CT. Water aggregate stability (WAS) was 0.84 kg kg -1 under NT compared to 0.81 kg kg -1 under CT. Similarly, soil organic carbon (SOC) and total nitrogen (TN) were greater under NT than under CT with SOC values for 0 to 60 cm of 96.0 and 91.0 Mg ha -1 and TN values of 8.87 and 8.40 Mg ha -1 for NT and CT, respectively. Rotations affected WAS, TN, and K levels with WAS being greatest for the CSW rotation at 0.87 kg kg -1, decreasing with more soybean years (CS, 0.82 kg kg -1 and SSS, 0.79 kg kg -1). A similar pattern was detected for TN and exchangeable K. Results indicated that while the use of NT improved soil quality, long-term implementation of continuous corn had similar soil quality parameters to those found under a corn-soybean rotation.
  • Authors:
    • Elshout,P. M. F.
    • van Zelm,R.
    • Balkovic,J.
    • Obersteiner,M.
    • Schmid,E.
    • Skalsky,R.
    • van der Velde,M.
    • Huijbregts,M. A. J.
  • Source: Nature Climate Change
  • Volume: 5
  • Issue: 6
  • Year: 2015
  • Summary: A global increase in the demand for crop-based biofuels may be met by cropland expansion, and could require the sacrifice of natural vegetation. Such land transformation alters the carbon and nitrogen cycles of the original system, and causes significant greenhouse-gas emissions, which should be considered when assessing the global warming performance of crop-based biofuels. As an indicator of this performance we propose the use of greenhouse-gas payback time (GPBT), that is, the number of years it takes before the greenhouse-gas savings due to displacing fossil fuels with biofuels equal the initial losses of carbon and nitrogen stocks from the original ecosystem. Spatially explicit global GPBTs were derived for biofuel production systems using five different feedstocks (corn, rapeseed, soybean, sugarcane and winter wheat), cultivated under no-input and high-input farm management. Overall, GPBTs were found to range between 1 and 162 years (95% range, median: 19 years) with the longest GPBTs occurring in the tropics. Replacing no-input with high-input farming typically shortened the GPBTs by 45 to 79%. Location of crop cultivation was identified as the primary factor driving variation in GPBTs. This study underscores the importance of using spatially explicit impact assessments to guide biofuel policy.
  • Authors:
    • Brookes,G.
    • Barfoot,P.
  • Source: GM Crops & Food
  • Volume: 7
  • Issue: 2
  • Year: 2015
  • Summary: This paper updates previous assessments of how crop biotechnology has changed the environmental impact of global agriculture. It focuses on the environmental impacts associated with changes in pesticide use and greenhouse gas emissions arising from the use of GM crops since their first widespread commercial use in the mid 1990s. The adoption of GM insect resistant and herbicide tolerant technology has reduced pesticide spraying by 553 million kg (-8.6%) and, as a result, decreased the environmental impact associated with herbicide and insecticide use on these crops (as measured by the indicator the Environmental Impact Quotient (EIQ)) by 19.1%. The technology has also facilitated important cuts in fuel use and tillage changes, resulting in a significant reduction in the release of greenhouse gas emissions from the GM cropping area. In 2013, this was equivalent to removing 12.4 million cars from the roads.
  • Authors:
    • N'Dayegamiye,A.
    • Whalen,J. K.
    • Tremblay,G.
    • Nyiraneza,J.
    • Grenier,M.
    • Drapeau,A.
    • Bipfubusa,M.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Legume crops leave N-rich residues and improve soil properties that can boost the yield of subsequent crops. This study conducted at two sites in Quebec, eastern Canada, identified the most appropriate preceding legume crops for subsequent corn ( Zea mays L.) and wheat ( Triticum aestivum L.) yield and N nutrition. Legumes were established in 2011, in monoculture or mixed with grain crops, for a total of 13 treatments: common bean ( Phaseolus vulgaris L.), soybean ( Glycine max L.), dry pea ( Pisum sativum L.), hairy vetch ( Vicia villosa Roth), alfalfa ( Medicago sativa L.), and crimson clover ( Trifolium incarnatum L.), (hairy vetch/wheat, crimson clover/wheat, field pea/wheat, alfalfa/corn, hairy vetch/corn, crimson clover/corn) and a non-N fixing crop (corn) as the control. In 2012, each plot was split and five N fertilizer rates applied to corn and wheat. Four legume systems (alfalfa, hairy vetch, crimson clover, and hairy vetch/wheat) significantly increased the soil structure stability, alkaline phosphatase and dehydrogenase activities at warmer St-Mathieu-de-Beloeil location but not at the cooler St-Lambert-de-Lauzon site. These legumes also significantly increased yields and N nutrition of corn and wheat at St Mathieu-de-Beloeil and of wheat only at St-Lambert-de-Lauzon. Although legume N credit was found low (~30 kg N ha -1), the N fertilizer replacement value was 51 to 77 kg N ha -1 for corn and up to 37 kg N ha -1 for wheat, depending on the preceding legume crop. This suggests that indirect effects related to improved soil properties impacted positively corn and wheat yield and N nutrition.
  • Authors:
    • Siebers,M. H.
    • Yendrek,C. R.
    • Drag,D.
    • Locke,A. M.
    • Acosta,L. R.
    • Leakey,A. D. B.
    • Ainsworth,E. A.
    • Bernacchi,C. J.
    • Ort,D. R.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 8
  • Year: 2015
  • Summary: Heat waves already have a large impact on crops and are predicted to become more intense and more frequent in the future. In this study, heat waves were imposed on soybean using infrared heating technology in a fully open-air field experiment. Five separate heat waves were applied to field-grown soybean ( Glycine max) in central Illinois, three in 2010 and two in 2011. Thirty years of historical weather data from Illinois were analyzed to determine the length and intensity of a regionally realistic heat wave resulting in experimental heat wave treatments during which day and night canopy temperatures were elevated 6°C above ambient for 3 days. Heat waves were applied during early or late reproductive stages to determine whether and when heat waves had an impact on carbon metabolism and seed yield. By the third day of each heat wave, net photosynthesis ( A), specific leaf weight (SLW), and leaf total nonstructural carbohydrate concentration (TNC) were decreased, while leaf oxidative stress was increased. However, A, SLW, TNC, and measures of oxidative stress were no different than the control ca. 12 h after the heat waves ended, indicating rapid physiological recovery from the high-temperature stress. That end of season seed yield was reduced (~10%) only when heat waves were applied during early pod developmental stages indicates the yield loss had more to do with direct impacts of the heat waves on reproductive process than on photosynthesis. Soybean was unable to mitigate yield loss after heat waves given during late reproductive stages. This study shows that short high-temperature stress events that reduce photosynthesis and increase oxidative stress resulted in significant losses to soybean production in the Midwest, U.S. The study also suggests that to mitigate heat wave-induced yield loss, soybean needs improved reproductive and photosynthetic tolerance to high but increasingly common temperatures.
  • Authors:
    • Sieverding,H. L.
    • Bailey,L. M.
    • Hengen,T. J.
    • Clay,D. E.
    • Stone,J. J.
  • Source: Journal of Environmental Quality
  • Volume: 44
  • Issue: 4
  • Year: 2015
  • Summary: Biofuel policy changes in the United States have renewed interest in soybean [ Glycine max (L.) Merr.] biodiesel. Past studies with varying methodologies and functional units can provide valuable information for future work. A meta-analysis of nine peer-reviewed soybean life cycle analysis (LCA) biodiesel studies was conducted on the northern Great Plains in the United States. Results of LCA studies were assimilated into a standardized system boundary and functional units for global warming (GWP), eutrophication (EP), and acidification (AP) potentials using biodiesel conversions from peer-reviewed and government documents. Factors not fully standardized included variations in N 2O accounting, mid- or end-point impacts, land use change, allocation, and statistical sampling pools. A state-by-state comparison of GWP lower and higher heating values (LHV, HHV) showed differences attributable to variations in spatial sampling and agricultural practices (e.g., tillage, irrigation). The mean GWP of LHV was 21.1 g.CO 2-eq MJ -1 including outliers, and median EP LHV and AP LHV was 0.019 g.PO 4-eq MJ -1 and 0.17 g.SO 2-eq MJ -1, respectively, using the limited data available. An LCA case study of South Dakota soybean-based biodiesel production resulted in GWP estimates (29 or 31 g.CO 2-eq MJ -1; 100% mono alkyl esters [first generation] biodiesel or 100% fatty acid methyl ester [second generation] biodiesel) similar to meta-analysis results (30.1 g.CO 2-eq MJ -1). Meta-analysis mean results, including outliers, resemble the California Low Carbon Fuel Standard for soybean biodiesel default value without land use change of 21.25 g.CO 2-eq MJ -1. Results were influenced by resource investment differences in water, fertilizer (e.g., type, application), and tillage. Future biofuel LCA studies should include these important factors to better define reasonable energy variations in regional agricultural management practices.